A diverse group of 10 investigators from 9 divisions at the Children's Hospital of Philadelphia are studying a variety of protein-protein interaction processes important for receptor biosynthesis, apoptosis, protein aggregation, blood cell development and vascular biology. Common to all these research programs is the need for quantitative measurements of protein-protein and protein-ligand interactions. We therefore request funds to purchase a Biacore 3000 system for measurements of kinetic binding parameters. This surface plasmon resonance technology is increasingly a technique of choice in many applications, because it requires small quantities of purified proteins in comparison to other techniques. The Biacore 3000 will be housed in our new Protein Core Facility and will complement mass spectrometry, analytical centrifugation and chromatography, to provide the community with a suite of protein interaction tools, that are currently not available on campus. The Biacore 3000 will operate on a recharge basis with additional support from the Children's Hospital of Philadelphia. It will be either a user-operated or a full-service system, depending on a user's choice. It will be overseen by Dr. M. Rosenblatt, the facility's director, working with the PI and Drs. Phillips, Ischiropoulos and Krishnashwamy, who constitute the steering committee. The major users will occupy approximately 75% of the instrument time, with remaining time made available to all Children's Hospital of Philadelphia researchers. [unreadable] [unreadable]